| abstract |
A stepped cannula (2) for supplying a material to the central nervous system, the stepped cannula having an outside diameter, a distal end, a proximal end and a lumen extending between the proximal and distal ends, the stepped cannula comprising two or more co-axially arranged segments, each of the segments having an outer diameter defining the outer diameter of the cannula, where the outer diameter of the segments is different, characterized in that a surface of the cannula that comes into contact with the material to be supplied is fused silica. |